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7

There are so many 'what tools' questions, do we really need another?
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ZoredacheJun 6 '09 at 9:49

4

I just have to ask: if no one's heard of a tool, then how will it get upvotes?
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quuxJun 7 '09 at 2:52

MTR (My Trace Route) is also a pretty good tool. It combines the functionality of the 'traceroute' and 'ping' programs in a single network diagnostic tool. Like traceroute except it gives more network quality and network diagnostic info. Leave running to get real time stats. Reports best and worst round trip times in milliseconds... It shows latency, jitter (average/best/worst): http://www.bitwizard.nl/mtr/

I use 'ss' which is part of the iproute package (which also includes the great ip and tc commands) to get information about tcp/udp sockets.
It supplies more information that the regular 'netstat' and can be used with filters, for instance:

I should mention that the two arping programs are available in most distributions and that they conflict. The one is a part of iproute2, and the other is independent. Wikipedia describes both; the arping I like is by Thomas Habets.
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MeiSep 16 '11 at 14:40

Windows: Nbtstat (has a variety of tricks, but -A to get the machine name of a remote IP can be really handy assuming you're in an environment where permissions will let this work)

All of the sysinternals tools, (process explorer, debug view, etc...). Particularly debug view, you'd be surprised how many server programs write interesting/useful things to the debug log and that's the only way I know to view it. Those are must-haves though.

Unix: strace/ktrace/truss Are my favorite tools (best non-obvious use, if a there's a process running that has it's stderr redirected to /dev/null and you don't want to stop it, monitor the calls to write on fd2.

lsof: (list of open files) I always forget about this one, but when you need it, you need it.

getmac is a bit hopeless IMHO. Does anyone know which interface "\Device\Tcpip_{72338DC1-13A4-8514-2C1B-60FC3B4559DB}" is off the top of their head? I prefer "ipconfig /all" or even a PowerShell one-liner like "get-wmiobject win32_networkadapter | format-table name,netconnectionid,macaddress".
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ThatGraemeGuyJun 6 '09 at 16:47

It's frequently just considered as part of the larger Puppet configuration management framework, but extremely useful in its own right; giving a consistent cross-platform way of finding out core system information. Great in shell scripts, essentially.

I'm going to go with a hacker tool, that might as well be useful to diagnose troubles: Cain. It can sniff a network and do a lot of attacks(arp poisoning, man in the middle,etc) on a network as well as breaking(or recovering) passwords.

One tool that I absolutely find indispensible is tcptraceroute [1] - this is a traceroute that does not use ICMP packets to perform timings, but uses TCP instead. This allows you to traceroute without regard to the typical blocking of ICMP: it works well.

scp - only mentioned because so few people use it, relying on FTP instead. I've always loved the ability to grab files instantly from remote hosts. Secure, quick, and doesn't need a dedicated daemon running.

I try not to use too many "nonstandard" tools. That is, tools that aren't easily available between operating systems or out of a particular distribution's software repository. I work on a Macbook, and I do testing on a variety of different Linux/Unix platforms.

That said, I like ohai(1). It is the node data collection tool used by Chef. It outputs data in JSON, so it can be manipulated with a variety of JSON parsing libraries. Since I work on Chef :-), it's a "nonstandard" tool available on every system I work with.

Odd answer in a way as it's not a tech tool directly - but I couldn't live without EverNote. It's a centralised note taking system, it has Windows, Mac, iPhone clients and lets you clip pits of web pages (with links to the original), has catergories, records images & voice notes.

It's not exactly a small cli tool as such, but I can heartily recommend Zenoss Core for network and system monitoring. It has restored my faith in monitoring-and-alerting software.

Where tools like Nagios, Cacti, etc. all have steep learning curves and seem to be good at only one thing, most often you have a need for an all-in-one solution, and Zenoss Core provides that for free (and Free).

It's hard to summarize, but basically it's an application with web-interface that autodiscovers devices on your network, then monitors tons of parameters, logfiles, ports, services, software, hardware, amount-of-pages-printed, etc. If anything fails or crosses a threshold you get an alert. It's easy to get started: enable/install snmp on each device you want to monitor, install Zenoss on a server, and open the web interface.

The free Core version is good enough for small and medium businesses, while the commercial Professional and Enterprise versions provide some advanced features.

If you ever thought about Nagios, Cacti or the like, be sure to evaluate Zenoss as well.